How to calculate international age
- Current year − birth year
- Subtract one if this year’s birthday has not come yet
You are 0 at birth and turn 1 on your first birthday.
Three ages you may hear about
For someone born on December 20, 2000, on October 3, 2026:
| Method | Rule | Age |
|---|---|---|
| International age | years since birth, changes on birthday | 25 (26 from Dec 20) |
| Year-based age | current year − birth year | 26 |
| Traditional Korean age | one at birth, plus one every Jan 1 | 27 (no longer used officially) |
Where year-based age remains
The Korean government said these areas keep year-based age for convenience:
| Area | Basis |
|---|---|
| Elementary school entry | birth year |
| Youth limits on buying alcohol and tobacco | year-based age |
| Military service screening | year-based age |
| Civil-service exam age limits | year-based age |
Rules that already used international age, such as voting at 18, retirement age and pensions, did not change.
Birthday countdown
Add birthdays with Yearly repeat
In D-Day Counter, enter the birth date, choose the Birthday category and set Repeat to Yearly. It shows the days left until the next birthday, the day your international age goes up.
Keep the family in one list
Sort by “Nearest” so the next birthday is on top. The sort button cycles through Nearest, Farthest and Added.
The app’s English screenshots below still show sample titles in Korean (an exam and a wedding anniversary).
FAQ
When does the app show a February 29 birthday in other years?
Yearly repeat uses February 28 in common years. See repeats on the 31st or Feb 29.
What about a lunar-calendar birthday?
Its solar date moves every year, so Yearly repeat will not match. See lunar birthday countdown.
Sources: Korea.kr, what changes under the international-age law (Korean)
D-Day Counter · Days Until / Since
No sign-up: just a title and a date. Everything stays on your phone. Free on Android, in English and Korean.